Hearing device and a hearing system comprising a multitude of adaptive two channel beamformers

ABSTRACT

A hearing system comprises a first hearing device, e.g. a hearing aid. The hearing system comprises at least three input transducers, one of which being selected as a reference input transducer providing a reference input signal, at least two adaptive 2-channel beamformers, each providing a spatially filtered signal based on first and second beamformer-input signals, wherein the adaptive 2-channel beamformers maintain unit amplitude and phase for a target component of said reference input signal. The at least two 2-channel beamformers are coupled in a layered structure at least comprising a primary layer and a secondary layer. The adaptive parameter of a given 2-channel beamformer is determined from the first and second beamformer-input signals for the 2-channel beamformer in question.

SUMMARY

The present disclosure deals with audio processing devices or systems,e.g. hearing aids, headsets, speakerphones or the like, and possibleauxiliary devices associated therewith, e.g. with which exchange of datacan be established.

An audio processing system may comprise at least two or at least threeinput transducers configured to convert sound in the environment of theaudio processing system, to respective at least three electric inputsignals, one of which being selected as a reference input transducerproviding a reference input signal, or a reference input signal beingdefined by an electric signal determined from said at least threeelectric input signals as if provided by a microphone located at aspatial reference point relative to locations of said at least threeinput transducers.

The at least two adaptive 2-channel beamformers, may each provide aspatially filtered signal based on first and second beamformer-inputsignals, wherein said adaptive 2-channel beamformers maintain unitamplitude and phase for a target component of said reference inputsignal. The at least two 2-channel beamformers may be coupled in acascaded structure at least comprising a primary layer and a secondarylayer. The primary layer may comprise at least one of the at least two2-channel beamformers, said at least one 2-channel beamformer of theprimary layer being termed primary 2-channel beamformer(s). Thesecondary layer may comprise at least another one of said at least two2-channel beamformers, said at least one 2-channel beamformer of thesecond layer being termed secondary 2-channel beamformer(s). The atleast two 2-channel beamformers may comprise a A) first primary2-channel beamformer, wherein said first beamformer-input signal is saidreference input signal, and wherein said second beamformer-input signalis selected among the remaining electric input signals, said firstprimary 2-channel beamformer providing a primary spatially filteredreference signal; and B) a first secondary 2-channel beamformer, whereinsaid first beamformer-input signal is said primary spatially filteredreference signal, and wherein said second beamformer-input signal isselected among a) those of said at least three electric input signals,which are not used as inputs to said first primary 2-channel beamformer,or among said at least two electric input signals, and b) a primaryspatially filtered signal from a possible further primary 2-channelbeamformer, said first secondary 2-channel beamformer providing asecondary spatially filtered reference signal. An adaptive parameter ofa given 2-channel beamformer may be determined from the first and secondbeamformer-input signals for said 2-channel beamformer.

A Hearing System:

In an aspect, the present disclosure deals with hearing devices, e.g.hearing aids, headsets, speakerphones or the like, and possibleauxiliary devices associated therewith, e.g. with which exchange of datacan be established.

In an aspect of the present application, a hearing system comprising afirst hearing device, e.g. a hearing aid, the first hearing device beingconfigured to be worn at or in a first ear of a user, or to be fully orpartially implanted in the head of the user at the first ear isprovided. The hearing system comprises

-   -   at least three input transducers configured to convert sound in        the environment of the hearing system to respective at least        three electric input signals, one of which being selected as a        reference input transducer providing a reference input signal,        or a reference input signal being defined by an electric signal        determined from said at least three electric input signals as if        provided by a microphone located at a spatial reference point        relative to locations of said at least three input transducers;    -   at least two adaptive 2-channel beamformers, each providing a        spatially filtered signal based on first and second        beamformer-input signals, wherein said adaptive 2-channel        beamformers maintain unit amplitude and phase for a target        component of said reference input signal;        -   said at least two 2-channel beamformers being coupled in a            layered structure at least comprising a primary layer and a            secondary layer,        -   where said primary layer comprises at least one of said at            least two 2-channel beamformers, termed primary 2-channel            beamformer(s); and        -   wherein said secondary layer comprises at least another one            of said at least two 2-channel beamformers, termed secondary            2-channel beamformer(s).        -   The at least two 2-channel beamformers may comprise        -   a first primary 2-channel beamformer, wherein said first            beamformer-input signal is said reference input signal, and            wherein said second beamformer-input signal is selected            among the remaining electric input signals, said first            primary 2-channel beamformer providing a primary spatially            filtered reference signal; and        -   a first secondary 2-channel beamformer, wherein said first            beamformer-input signal is said primary spatially filtered            reference signal, and wherein said second beamformer-input            signal is selected among a) those of said at least three            electric input signals, which are not used as inputs to said            first primary 2-channel beamformer, and b) a primary            spatially filtered signal from a possible further primary            2-channel beamformer, said first secondary 2-channel            beamformer providing a secondary spatially filtered            reference signal, and        -   wherein an adaptive parameter of a given 2-channel            beamformer is determined from the first and second            beamformer-input signals for said 2-channel beamformer.

Thereby an improved hearing system may be provided.

The adaptive parameter of a given 2-channel beamformer may be determined(e.g. solely) from the first and second beamformer-input signals for the2-channel beamformer in question.

An advantage of the hearing system according to the present disclosureis that the adaptive 2-channel beamformers maintain unit amplitude andphase for a target component of said reference input signal, so thatnoise reduction is performed with an unchanged target direction. Thedirection to the target sound source as experienced at the referenceinput (e.g. at the reference microphone or a virtual referencemicrophone) is maintained through the cascaded 2-channel beamformerstructure (so that target signal components remain unchanged).

Properties of the virtual microphone (virtual reference point) may e.g.obtained off-line by measuring the transfer function to a microphonelocated at the desired (reference) position (which is not a location ofa microphone of the final (physically implemented) microphone array)with respect to the other microphones in the microphone array. This isillustrated in FIG. 9.

The main motivation of using multiple 2-input beamformers instead of oneM-input beamformers is the reduction in complexity in the adaptation ofthe β-parameter based on the noise covariance. In a 2-input GeneralizedSidelobe Canceller (GSC), the β-parameter is a scalar, defined by

${\beta_{opt} = \frac{w_{O}^{H}C_{v}w_{C}}{w_{C}^{H}C_{v}w_{C}}},$

where the division operation between two scalar values has the largestinfluence on the computational complexity.

In an M>2 GSC, the β-parameter is an (M−1)×1 size vector, defined by

β_(opt)=(W _(C) ^(H) C _(v) W _(C))⁻¹ W _(C) ^(H) C _(v) W _(O),

where W_(C) ^(H) is known as a size (M−1)×M blocking matrix and W_(O) isan M×1 beamformer vector. The main influence on the complexity is the(M−1) size matrix inverse operation, which is more expensive than M−1(e.g. two for M=3) divisions (one division per 2-channel beamformer).

The proposed structure only requires the additional computationcomplexity of a single division for every extra microphone with 2-inputbeamformer added in the structure. When using a full GSC, the complexityincreases exponentially as a function of the number of microphones:O((M−1)³).

The first and/or secondary 2-channel beamformers may be implemented asrespective minimum variance distortionless response (MVDR) beamformers.

The term ‘selected among the remaining electric input signals’ is in thepresent context intended to mean ‘selected among the at least threeelectric input signals, except the reference signal’.

The first primary two-channel beamformer is configured to maintain thetarget signal component (amplitude/magnitude and phase) picked up by thereference input transducer and provided in the reference signal (and toattenuate noise from other directions than the target signal). Thetarget signal is e.g. provided by a localized sound source, e.g. in theform of a speech signal of a talking person.

The adaptive parameter(s), e.g. a parameter e.g. a frequency dependentparameter β(k), where k is a frequency index, of each of the 2-channelbeamformers are ‘autonomously’ determined (i.e. only in dependence ofits own first and second beamformer-input signals).

In the present context, the term ‘a layered structure of 2-channelbeamformers’ is taken to mean that the 2-channel beamformers arecascaded, so that outputs of a 2-channel beamformer of a given layer(e.g. the 1^(st) (or primary) layer) is used as input to a 2-channelbeamformer of a subsequent layer (e.g. the 2^(nd) (or secondary) layer).The term ‘a layered structure of 2-channel beamformers’ may be taken tobe equivalent to the term ‘a cascaded coupling of 2-channelbeamformers’.

The layered structure of 2-channel beamformers may comprise more thantwo layers, primary, secondary, tertiary, etc., as e.g. indicated inFIG. 3. In a three-layered structure, the secondary spatially filteredreference signal is used as a first beamformer-input signal to a firsttertiary 2-channel beamformer, etc.

The hearing system may comprise at least three input transducers, whichwhen worn by the user are located two and two on first, second and thirdstraight lines, which together form a triangle. In this embodiment, thethree input transducers are not located on one straight line. At leasttwo of the at least three input transducers may be located on a straightline having an extension in a direction towards a mouth of the user,when wearing the hearing system. Thereby a (primary) 2-channelbeamformer with a target direction towards the user's mouth (and thusparticularly suitable for picking up the voice of the user (‘own voice’)may be implemented. In an embodiment, at least one, such as two of the(at least) three input transducers are located in a BTE-part of thehearing device adapted to be located at or behind the external ear(pinna) of the user (or in concha). In an embodiment, one of the (atleast) three input transducers is(are) located in or at an ear canal ofthe user (or elsewhere around the ear). This has the advantage ofallowing ‘out of horizontal plane’ beamforming, e.g. directed towardssound coming from above or below the user wearing the hearing device(s).It may as well, however, allow better beamforming in the horizontalplane, even though none of the microphones are located in the horizontalplane. In an embodiment, at least one of the input transducers islocated in another device, e.g. separate from the hearing device inquestion, e.g. in another body worn device, e.g. in a hearing devicelocated at or in the opposite ear of the user, or in a separatemicrophone unit, e.g. of a communication device (e.g. a smartphone), ora remote control device. The hearing system may be configured to pick upthe user's own voice in a particular communication-mode of operation. Inthis mode of operation, the hearing system may be configured to receivean input audio signal from another device (e.g. a telephone or similardevice), e.g. representing a voice of a communication partner.

The hearing system may comprise at least three input transducers, whichwhen worn by the user are located on a straight line. In an embodiment,the three input transducers constitute a linear array having a fixeddistance between neighbouring input transducers of the array.

In an embodiment, the hearing system, e.g. the (first) hearing device,comprises just three input transducers.

The hearing system may comprise at least two primary 2-channelbeamformers.

The layered structure (cascaded coupling) of the hearing system maycomprise at least three 2-channel beamformers, e.g. distributed inrespective primary, secondary and tertiary layers.

The hearing system may comprise a second hearing device, e.g. a hearingaid, the second hearing device being configured to be worn at or in asecond ear of the user, or to be fully or partially implanted in thehead of the user at the second ear, wherein at least one of said atleast three input transducers is located in the second hearing device.The first and second hearing devices may each comprise appropriateantenna and transceiver circuitry configured to allow the establishmentof a communication link between them exchange information (e.g. audiosignals, such as electric input signals from an input transducer)between them. The at least three input transducers of the hearing systemmay be distributed over the first and second hearing devices. Each ofthe first and second hearing devices may comprise two or three or moreinput transducers.

In an embodiment, an input transducer is or comprises a microphone.

The hearing system may comprise a detection unit for determining a soundsource location encoding parameter indicative of a location of or adirection of arrival to said target sound source. Identification andlocation of or a target direction to a target sound source (e.g. aperson speaking) can be estimated in a number of ways, cf. e.g.EP3413589A1. The sound source location encoding parameter may e.g. bedetermined as or based on a covariance estimate between said electricinput signals, e.g. two and two, e.g. between each combination twoelectric input signals selected among the at least three electric inputsignals of the hearing system. The sound source location encodingparameter may e.g. be determined as or based on a direction of arrival.

The detection unit may be configured to determine the sound sourcelocation encoding parameter as, or based on, a covariance estimatebetween the electric input signals.

The hearing system may comprise a user interface allowing a user toindicate a location of or a direction of arrival to the target soundsource. The user interface may e.g. be implemented as an APP of a remotecontrol or a smartphone, or similar body worn device, e.g. a device wornon an arm, e.g. a smartwatch. The hearing system may be configured toextract a sound source location encoding parameter from the indicationon the user interface.

The hearing system may comprise a controller for automatically selectingsaid second beamformer-input signals of the first primary and firstsecondary 2-channel beamformers, respectively. The secondbeamformer-input signals may e.g. be selected in dependence of anestimated or expected direction of arrival of a target signal componentof the sound in the environment.

The hearing system may be configured to provide that the secondbeamformer-input signals of the first primary and first secondary2-channel beamformers, respectively, are determined from the soundsource location encoding parameter or from a user's indication on theuser interface.

The hearing system may comprise a memory comprising corresponding valuesof a) a target sound source location or direction of arrival and b)appropriate coupling configurations of the available input transducersto 2-channel beamformers of the hearing system. The memory may e.g.contain data that allow a selection of an appropriate coupling ofelectric input signals to the respective primary, secondary, etc.,2-channel beamformers to be made in dependence of the (target) soundsource location encoding parameter, e.g. the direction of arrival.

The hearing system may be arranged to provide that the (first and/orsecond) hearing device is(are) constituted by or comprises a hearingaid, a headset, an earphone, an ear protection device or a combinationthereof. The hearing system may comprise a spectacle frame or othercarrier. The spectacle frame or other carrier may comprise one or moreof the input transducers, e.g. microphones. The input transducers maye.g. be located on one or both side bars, and/or on a cross-bar of thespectacle frame. The spectacle frame may e.g. support glasses to enhancea user's eye sight.

The hearing system may comprise a (first) hearing device and anauxiliary device. The auxiliary device may as well contain a cascadedbeamformer according to the present disclosure.

The hearing system may be adapted to establish a communication linkbetween the hearing device or hearing devices and the auxiliary deviceto provide that information, e.g. control and status signals, andpossibly audio signals, can be exchanged or forwarded from one to theother.

The auxiliary device may comprise the user interface.

The 2-channel beamformer may be optimized as a hardware block. Thefunction of a 2-channel beamformer may e.g. be optimized as a standardcell in a component library for a given semiconductor process. This hasthe advantage that the properties of the 2-channel beamformer can beoptimized (e.g. with respect to delay) and easily duplicated indifferent parts of the hearing system (e.g. in a given (ASIC)processor-circuit of a hearing device or other processing device).

In an embodiment, the hearing system is adapted to establish acommunication link between the hearing device and the auxiliary deviceto provide that information (e.g. control and status signals, possiblyaudio signals) can be exchanged or forwarded from one to the other.

In an embodiment, the hearing system comprises an auxiliary device, e.g.a remote control, a smartphone, or other portable or wearable electronicdevice, such as a smartwatch or the like.

In an embodiment, the auxiliary device is or comprises a remote controlfor controlling functionality and operation of the hearing device(s). Inan embodiment, the function of a remote control is implemented in asmartphone, the smartphone possibly running an APP allowing to controlthe functionality of the hearing system via the smartphone (the hearingdevice(s) comprising an appropriate wireless interface to thesmartphone, e.g. based on Bluetooth or some other standardized orproprietary scheme).

In an embodiment, the auxiliary device is or comprises an audio gatewaydevice adapted for receiving a multitude of audio signals (e.g. from anentertainment device, e.g. a TV or a music player, a telephoneapparatus, e.g. a mobile telephone or a computer, e.g. a PC) and adaptedfor selecting and/or combining an appropriate one of the received audiosignals (or combination of signals) for transmission to the hearingdevice.

In an embodiment, the auxiliary device is or comprises another hearingdevice. In an embodiment, the hearing system comprises two hearingdevices adapted to implement a binaural hearing system, e.g. a binauralhearing aid system.

A Hearing Device:

In an embodiment, the hearing device is adapted to provide a frequencydependent gain and/or a level dependent compression and/or atransposition (with or without frequency compression) of one or morefrequency ranges to one or more other frequency ranges, e.g. tocompensate for a hearing impairment of a user. In an embodiment, thehearing device comprises a signal processor for enhancing the inputsignals and providing a processed output signal

In an embodiment, the hearing device comprises an output unit forproviding a stimulus perceived by the user as an acoustic signal basedon a processed electric signal. In an embodiment, the output unitcomprises a number of electrodes of a cochlear implant (for a CI typehearing device) or a vibrator of a bone conducting hearing device. In anembodiment, the output unit comprises an output transducer. In anembodiment, the output transducer comprises a receiver (loudspeaker) forproviding the stimulus as an acoustic signal to the user (e.g. in anacoustic (air conduction based) hearing device). In an embodiment, theoutput transducer comprises a vibrator for providing the stimulus asmechanical vibration of a skull bone to the user (e.g. in abone-attached or bone-anchored hearing device).

In an embodiment, the hearing device comprises an input unit forproviding an electric input signal representing sound. In an embodiment,the input unit comprises an input transducer, e.g. a microphone, forconverting an input sound to an electric input signal. In an embodiment,the input unit comprises a wireless receiver for receiving a wirelesssignal comprising sound and for providing an electric input signalrepresenting said sound.

The hearing device comprises a directional microphone system adapted tospatially filter sounds from the environment, and thereby enhance atarget acoustic source among a multitude of acoustic sources in thelocal environment of the user wearing the hearing device. In anembodiment, the directional system is adapted to detect (such asadaptively detect) from which direction a particular part of themicrophone signal originates. This can be achieved in various differentways as e.g. described in the prior art. In hearing devices, amicrophone array beamformer is often used for spatially attenuatingbackground noise sources. Many beamformer variants can be found inliterature. The minimum variance distortionless response (MVDR)beamformer is widely used in microphone array signal processing. Ideallythe MVDR beamformer keeps the signals from the target direction (alsoreferred to as the look direction) unchanged, while attenuating soundsignals from other directions maximally. The generalized sidelobecanceller (GSC) structure is an equivalent representation of the MVDRbeamformer offering computational and numerical advantages over a directimplementation in its original form.

In an embodiment, the hearing device comprises an antenna andtransceiver circuitry (e.g. a wireless receiver) for wirelesslyreceiving a direct electric input signal from another device, e.g. froman entertainment device (e.g. a TV-set), a communication device, awireless microphone, or another hearing device. In an embodiment, thedirect electric input signal represents or comprises an audio signaland/or a control signal and/or an information signal.

Preferably, communication between the hearing device and the otherdevice is based on some sort of modulation at frequencies above 100 kHz.Preferably, frequencies used to establish a communication link betweenthe hearing device and the other device is below 70 GHz, e.g. located ina range from 50 MHz to 70 GHz, e.g. above 300 MHz, e.g. in an ISM rangeabove 300 MHz, e.g. in the 900 MHz range or in the 2.4 GHz range or inthe 5.8 GHz range or in the 60 GHz range (ISM=Industrial, Scientific andMedical, such standardized ranges being e.g. defined by theInternational Telecommunication Union, ITU). In an embodiment, thewireless link is based on a standardized or proprietary technology. Inan embodiment, the wireless link is based on Bluetooth technology (e.g.Bluetooth Low-Energy technology).

In an embodiment, the hearing device is a portable device, e.g. a devicecomprising a local energy source, e.g. a battery, e.g. a rechargeablebattery.

In an embodiment, the hearing device comprises a forward or signal pathbetween an input unit (e.g. an input transducer, such as a microphone ora microphone system and/or direct electric input (e.g. a wirelessreceiver)) and an output unit, e.g. an output transducer. In anembodiment, the signal processor is located in the forward path. In anembodiment, the signal processor is adapted to provide a frequencydependent gain according to a user's particular needs. In an embodiment,the hearing device comprises an analysis path comprising functionalcomponents for analyzing the input signal (e.g. determining a level, amodulation, a type of signal, an acoustic feedback estimate, etc.). Inan embodiment, some or all signal processing of the analysis path and/orthe signal path is conducted in the frequency domain. In an embodiment,some or all signal processing of the analysis path and/or the signalpath is conducted in the time domain.

In an embodiment, an analogue electric signal representing an acousticsignal is converted to a digital audio signal in an analogue-to-digital(AD) conversion process, where the analogue signal is sampled with apredefined sampling frequency or rate f_(s), f_(s) being e.g. in therange from 8 kHz to 48 kHz (adapted to the particular needs of theapplication) to provide digital samples x_(n) (or x[n]) at discretepoints in time t_(n) (or n), each audio sample representing the value ofthe acoustic signal at by a predefined number N_(b) of bits, N_(b) beinge.g. in the range from 1 to 48 bits, e.g. 24 bits. Each audio sample ishence quantized using N_(b) bits (resulting in 2^(Nb) different possiblevalues of the audio sample). A digital sample x has a length in time of1/f_(s), e.g. 50 μs, for f_(s)=20 kHz. In an embodiment, a number ofaudio samples are arranged in a time frame. In an embodiment, a timeframe comprises 64 or 128 audio data samples. Other frame lengths may beused depending on the practical application.

In an embodiment, the hearing devices comprise an analogue-to-digital(AD) converter to digitize an analogue input (e.g. from an inputtransducer, such as a microphone) with a predefined sampling rate, e.g.20 kHz. In an embodiment, the hearing devices comprise adigital-to-analogue (DA) converter to convert a digital signal to ananalogue output signal, e.g. for being presented to a user via an outputtransducer.

In an embodiment, the hearing device, e.g. the microphone unit, and orthe transceiver unit comprise(s) a TF-conversion unit for providing atime-frequency representation of an input signal. In an embodiment, thetime-frequency representation comprises an array or map of correspondingcomplex or real values of the signal in question in a particular timeand frequency range. In an embodiment, the TF conversion unit comprisesa filter bank for filtering a (time varying) input signal and providinga number of (time varying) output signals each comprising a distinctfrequency range of the input signal. In an embodiment, the TF conversionunit comprises a Fourier transformation unit for converting a timevariant input signal to a (time variant) signal in the (time-)frequencydomain. In an embodiment, the frequency range considered by the hearingdevice from a minimum frequency f_(min) to a maximum frequency f_(max)comprises a part of the typical human audible frequency range from 20 Hzto 20 kHz, e.g.

a part of the range from 20 Hz to 12 kHz. Typically, a sample rate f_(s)is larger than or equal to twice the maximum frequency f_(max),f_(s)≥2f_(max). In an embodiment, a signal of the forward and/oranalysis path of the hearing device is split into a number NI offrequency bands (e.g. of uniform width), where NI is e.g. larger than 5,such as larger than 10, such as larger than 50, such as larger than 100,such as larger than 500, at least some of which are processedindividually. In an embodiment, the hearing device is/are adapted toprocess a signal of the forward and/or analysis path in a number NP ofdifferent frequency channels (NP≤NI). The frequency channels may beuniform or non-uniform in width (e.g. increasing in width withfrequency), overlapping or non-overlapping.

In an embodiment, the hearing device comprises a number of detectorsconfigured to provide status signals relating to a current physicalenvironment of the hearing device (e.g. the current acousticenvironment), and/or to a current state of the user wearing the hearingdevice, and/or to a current state or mode of operation of the hearingdevice. Alternatively or additionally, one or more detectors may formpart of an external device in communication (e.g. wirelessly) with thehearing device. An external device may e.g. comprise another hearingdevice, a remote control, and audio delivery device, a telephone (e.g. asmartphone), an external sensor, etc.

In an embodiment, one or more of the number of detectors operate(s) onthe full band signal (time domain). In an embodiment, one or more of thenumber of detectors operate(s) on band split signals ((time-) frequencydomain), e.g. in a limited number of frequency bands.

In an embodiment, the number of detectors comprises a level detector forestimating a current level of a signal of the forward path. In anembodiment, the predefined criterion comprises whether the current levelof a signal of the forward path is above or below a given (L-)thresholdvalue. In an embodiment, the level detector operates on the full bandsignal (time domain) In an embodiment, the level detector operates onband split signals ((time-) frequency domain)

In a particular embodiment, the hearing device comprises a voicedetector (VD) for estimating whether or not (or with what probability)an input signal comprises a voice signal (at a given point in time). Avoice signal is in the present context taken to include a speech signalfrom a human being. It may also include other forms of utterancesgenerated by the human speech system (e.g. singing). In an embodiment,the voice detector unit is adapted to classify a current acousticenvironment of the user as a VOICE or NO-VOICE environment. This has theadvantage that time segments of the electric microphone signalcomprising human utterances (e.g. speech) in the user's environment canbe identified, and thus separated from time segments only (or mainly)comprising other sound sources (e.g. artificially generated noise). Inan embodiment, the voice detector is adapted to detect as a VOICE alsothe user's own voice. Alternatively, the voice detector is adapted toexclude a user's own voice from the detection of a VOICE.

In an embodiment, the hearing device comprises an own voice detector forestimating whether or not (or with what probability) a given input sound(e.g. a voice, e.g. speech) originates from the voice of the user of thesystem. In an embodiment, a microphone system of the hearing device isadapted to be able to differentiate between a user's own voice andanother person's voice and possibly from NON-voice sounds.

In an embodiment, the number of detectors comprises a movement detector,e.g. an acceleration sensor. In an embodiment, the movement detector isconfigured to detect movement of the user's facial muscles and/or bones,e.g. due to speech or chewing (e.g. jaw movement) and to provide adetector signal indicative thereof.

In an embodiment, the hearing device comprises a classification unitconfigured to classify the current situation based on input signals from(at least some of) the detectors, and possibly other inputs as well. Inthe present context ‘a current situation’ is taken to be defined by oneor more of

a) the physical environment (e.g. including the current electromagneticenvironment, e.g. the occurrence of electromagnetic signals (e.g.comprising audio and/or control signals) intended or not intended forreception by the hearing device, or other properties of the currentenvironment than acoustic);

b) the current acoustic situation (input level, feedback, etc.), and

c) the current mode or state of the user (movement, temperature,cognitive load, etc.);

d) the current mode or state of the hearing device (program selected,time elapsed since last user interaction, etc.) and/or of another devicein communication with the hearing device.

In an embodiment, the hearing device further comprises other relevantfunctionality for the application in question, e.g. compression, noisereduction, etc.

In an embodiment, the hearing device comprises a listening device, e.g.a hearing aid, e.g. a hearing instrument, e.g. a hearing instrumentadapted for being located at the ear or fully or partially in the earcanal of a user, e.g. a headset, an earphone, an ear protection deviceor a combination thereof. In an embodiment, the hearing assistancesystem comprises a speakerphone (comprising a number of inputtransducers and a number of output transducers, e.g. for use in an audioconference situation), e.g. comprising a beamformer filtering unit, e.g.providing multiple beamforming capabilities.

Use:

In an aspect, use of a hearing device as described above, in the‘detailed description of embodiments’ and in the claims, is moreoverprovided. In an embodiment, use is provided in a system comprising audiodistribution. In an embodiment, use is provided in a system comprisingone or more hearing aids (e.g. hearing instruments), headsets, earphones, active ear protection systems, etc., e.g. in handsfree telephonesystems, teleconferencing systems (e.g. including a speakerphone),public address systems, karaoke systems, classroom amplificationsystems, etc.

An APP:

In a further aspect, a non-transitory application, termed an APP, isfurthermore provided by the present disclosure. The APP comprisesexecutable instructions configured to be executed on an auxiliary deviceto implement a user interface for a hearing device or a hearing systemdescribed above in the ‘detailed description of embodiments’, and in theclaims. In an embodiment, the APP is configured to run on cellularphone, e.g. a smartphone, or on another portable device allowingcommunication with said hearing device or said hearing system.

The hearing system (including the auxiliary device, and the APP) may beadapted to allow a user to indicate a location of or direction to atarget sound source of current interest to the user. Thereby thedetermination of a currently appropriate (beneficial) couplingconfiguration of the electric input signals to the cascaded 2-channelbeamformers can be facilitated, including a choice of reference inputtransducer (and corresponding reference input signal). The APP may haveaccess to a database or dictionary (stored in a memory of the hearingsystem, e.g. of the auxiliary device) of corresponding appropriatereference input transducer and coupling configuration for a number ofdifferent locations of or directions to the target sound source(relative to the user).

A Method of Operating an Audio Processing Device or System:

In an aspect of the present application, a method of operating an audioprocessing device or system, e.g. a hearing device or a hearing system.The method comprises

-   -   providing at least three electric input signals representative        of sound in the environment of the audio processing device or        system, one of which being selected as a reference input        providing a reference input signal, or a reference input signal        being defined by an electric signal determined from said at        least three electric input signals as if provided by an input        located at a spatial reference point relative to locations of        inputs providing said at least three electric input signals;    -   providing at least two adaptive 2-channel beamformers, each        providing a spatially filtered signal based on first and second        beamformer-input signals, wherein said adaptive 2-channel        beamformers maintain unit amplitude and phase for a target        component of said reference input signal; and        -   providing that said at least two 2-channel beamformers are            coupled in a cascaded structure at least comprising a            primary layer and a secondary layer,        -   providing that said primary layer comprises at least one of            said at least two 2-channel beamformers, said at least one            beamformer of the primary layer being termed primary            2-channel beamformer(s); and        -   providing that said secondary layer comprises at least            another one of said at least two 2-channel beamformers, said            at least one beamformer of the second layer being termed            secondary 2-channel beamformer(s).    -   providing that said at least two adaptive 2-channel beamformers        comprise        -   a first primary 2-channel beamformer, wherein said first            beamformer-input signal is said reference input signal, and            wherein said second beamformer-input signal is selected            among the remaining electric input signals, said first            primary 2-channel beamformer providing a primary spatially            filtered reference signal; and        -   a first secondary 2-channel beamformer, wherein said first            beamformer-input signal is said primary spatially filtered            reference signal, and wherein said second beamformer-input            signal is selected among a) those of said at least three            electric input signals, which are not used as inputs to said            first primary 2-channel beamformer, and b) a primary            spatially filtered signal from a possible further primary            2-channel beamformer, said first secondary 2-channel            beamformer providing a secondary spatially filtered            reference signal, and        -   determining an adaptive parameter of a given 2-channel            beamformer from the first and second beamformer-input            signals for said 2-channel beamformer.

It is intended that some or all of the structural features of the deviceor system described above, in the ‘detailed description of embodiments’or in the claims can be combined with embodiments of the method, whenappropriately substituted by a corresponding process and vice versa.Embodiments of the method have the same advantages as the correspondingdevices or systems.

Definitions

In the present context, a ‘hearing device’ refers to a device, such as ahearing aid, e.g. a hearing instrument, or an active ear-protectiondevice, or other audio processing device, which is adapted to improve,augment and/or protect the hearing capability of a user by receivingacoustic signals from the user's surroundings, generating correspondingaudio signals, possibly modifying the audio signals and providing thepossibly modified audio signals as audible signals to at least one ofthe user's ears. A ‘hearing device’ further refers to a device such asan earphone or a headset adapted to receive audio signalselectronically, possibly modifying the audio signals and providing thepossibly modified audio signals as audible signals to at least one ofthe user's ears. Such audible signals may e.g. be provided in the formof acoustic signals radiated into the user's outer ears, acousticsignals transferred as mechanical vibrations to the user's inner earsthrough the bone structure of the user's head and/or through parts ofthe middle ear as well as electric signals transferred directly orindirectly to the cochlear nerve of the user.

The hearing device may be configured to be worn in any known way, e.g.as a unit arranged behind the ear with a tube leading radiated acousticsignals into the ear canal or with an output transducer, e.g. aloudspeaker, arranged close to or in the ear canal, as a unit entirelyor partly arranged in the pinna and/or in the ear canal, as a unit, e.g.a vibrator, attached to a fixture implanted into the skull bone, as anattachable, or entirely or partly implanted, unit, etc. The hearingdevice may comprise a single unit or several units communicatingelectronically with each other. The loudspeaker may be arranged in ahousing together with other components of the hearing device, or may bean external unit in itself (possibly in combination with a flexibleguiding element, e.g. a dome-like element).

More generally, a hearing device comprises an input transducer forreceiving an acoustic signal from a user's surroundings and providing acorresponding input audio signal and/or a receiver for electronically(i.e. wired or wirelessly) receiving an input audio signal, a (typicallyconfigurable) signal processing circuit (e.g. a signal processor, e.g.comprising a configurable (programmable) processor, e.g. a digitalsignal processor) for processing the input audio signal and an outputunit for providing an audible signal to the user in dependence on theprocessed audio signal. The signal processor may be adapted to processthe input signal in the time domain or in a number of frequency bands.In some hearing devices, an amplifier and/or compressor may constitutethe signal processing circuit. The signal processing circuit typicallycomprises one or more (integrated or separate) memory elements forexecuting programs and/or for storing parameters used (or potentiallyused) in the processing and/or for storing information relevant for thefunction of the hearing device and/or for storing information (e.g.processed information, e.g. provided by the signal processing circuit),e.g. for use in connection with an interface to a user and/or aninterface to a programming device. In some hearing devices, the outputunit may comprise an output transducer, such as e.g. a loudspeaker forproviding an air-borne acoustic signal or a vibrator for providing astructure-borne or liquid-borne acoustic signal. In some hearingdevices, the output unit may comprise one or more output electrodes forproviding electric signals (e.g. a multi-electrode array forelectrically stimulating the cochlear nerve). In an embodiment, thehearing device comprises a speakerphone (comprising a number of inputtransducers and a number of output transducers, e.g. for use in an audioconference situation).

In some hearing devices, the vibrator may be adapted to provide astructure-borne acoustic signal transcutaneously or percutaneously tothe skull bone. In some hearing devices, the vibrator may be implantedin the middle ear and/or in the inner ear. In some hearing devices, thevibrator may be adapted to provide a structure-borne acoustic signal toa middle-ear bone and/or to the cochlea. In some hearing devices, thevibrator may be adapted to provide a liquid-borne acoustic signal to thecochlear liquid, e.g. through the oval window. In some hearing devices,the output electrodes may be implanted in the cochlea or on the insideof the skull bone and may be adapted to provide the electric signals tothe hair cells of the cochlea, to one or more hearing nerves, to theauditory brainstem, to the auditory midbrain, to the auditory cortexand/or to other parts of the cerebral cortex.

A hearing device, e.g. a hearing aid, may be adapted to a particularuser's needs, e.g. a hearing impairment. A configurable signalprocessing circuit of the hearing device may be adapted to apply afrequency and level dependent compressive amplification of an inputsignal. A customized frequency and level dependent gain (amplificationor compression) may be determined in a fitting process by a fittingsystem based on a user's hearing data, e.g. an audiogram, using afitting rationale (e.g. adapted to speech). The frequency and leveldependent gain may e.g. be embodied in processing parameters, e.g.uploaded to the hearing device via an interface to a programming device(fitting system), and used by a processing algorithm executed by theconfigurable signal processing circuit of the hearing device.

A ‘hearing system’ refers to a system comprising one or two hearingdevices, and a ‘binaural hearing system’ refers to a system comprisingtwo hearing devices and being adapted to cooperatively provide audiblesignals to both of the user's ears. Hearing systems or binaural hearingsystems may further comprise one or more ‘auxiliary devices’, whichcommunicate with the hearing device(s) and affect and/or benefit fromthe function of the hearing device(s). Auxiliary devices may be e.g.remote controls, audio gateway devices, mobile phones (e.g.smartphones), or music players. Hearing devices, hearing systems orbinaural hearing systems may e.g. be used for compensating for ahearing-impaired person's loss of hearing capability, augmenting orprotecting a normal-hearing person's hearing capability and/or conveyingelectronic audio signals to a person. Hearing devices or hearing systemsmay e.g. form part of or interact with public-address systems, activeear protection systems, handsfree telephone systems, car audio systems,entertainment (e.g. karaoke) systems, teleconferencing systems,classroom amplification systems, etc.

Embodiments of the disclosure may e.g. be useful in applications such asapplications.

BRIEF DESCRIPTION OF DRAWINGS

The aspects of the disclosure may be best understood from the followingdetailed description taken in conjunction with the accompanying figures.The figures are schematic and simplified for clarity, and they just showdetails to improve the understanding of the claims, while other detailsare left out. Throughout, the same reference numerals are used foridentical or corresponding parts. The individual features of each aspectmay each be combined with any or all features of the other aspects.These and other aspects, features and/or technical effect will beapparent from and elucidated with reference to the illustrationsdescribed hereinafter in which:

FIG. 1A shows a first embodiment of a hearing system comprising threeinput transducers and two cascaded two channel beamformers according tothe present disclosure,

FIG. 1B shows a second embodiment of a hearing system comprising threeinput transducers and two cascaded two channel beamformers according tothe present disclosure,

FIG. 1C shows a third embodiment of a hearing system comprising threeinput transducers and two cascaded two channel beamformers according tothe present disclosure,

FIG. 1D shows a first embodiment of a hearing system comprising threeinput transducers and three channel beamformers according to the presentdisclosure, and

FIG. 1E shows a second embodiment of a hearing system comprising threeinput transducers and three channel beamformers according to the presentdisclosure,

FIG. 2A shows a first embodiment of a hearing system comprising firstand second hearing devices according to the present disclosure, and

FIG. 2B shows a second embodiment of a hearing system comprising firstand second hearing devices according to the present disclosure,specifically suitable for pick up of a user's own voice,

FIG. 3 shows an embodiment of a hearing system comprising fourmicrophones according to the present disclosure,

FIG. 4 shows an embodiment of a hearing device according to the presentdisclosure,

FIG. 5 shows an embodiment of an adaptive two-channel beamformer forproviding a beamformed signal based on two (microphone) beamformer-inputsignals,

FIG. 6 shows an embodiment of an M-input hearing system comprising M−1cascaded two-channel beamformers, each M−1-input transducer beingcoupled to an analysis filter bank to provide the electric input signalas a number of frequency sub-band signals,

FIG. 7A shows a first exemplary location of three microphones in aBTE-part of a hearing device according to the present disclosure, and

FIG. 7B shows a second exemplary location of three microphones in aBTE-part of a hearing device according to the present disclosure,

FIG. 8A illustrates an embodiment of a hearing system, e.g. a binauralhearing aid system, according to the present disclosure; and

FIG. 8B illustrates an auxiliary device configured to execute an APP forselecting a mode of operation of the hearing system where a location ofor a direction to a target sound source of current interest to the usercan be shown and/or indicated, and

FIG. 9 illustrates the location of a virtual reference microphone in ahearing device according to the present disclosure.

The figures are schematic and simplified for clarity, and they just showdetails which are essential to the understanding of the disclosure,while other details are left out. Throughout, the same reference signsare used for identical or corresponding parts.

Further scope of applicability of the present disclosure will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the disclosure, aregiven by way of illustration only. Other embodiments may become apparentto those skilled in the art from the following detailed description.

DETAILED DESCRIPTION OF EMBODIMENTS

The detailed description set forth below in connection with the appendeddrawings is intended as a description of various configurations. Thedetailed description includes specific details for the purpose ofproviding a thorough understanding of various concepts. However, it willbe apparent to those skilled in the art that these concepts may bepracticed without these specific details. Several aspects of theapparatus and methods are described by various blocks, functional units,modules, components, circuits, steps, processes, algorithms, etc.(collectively referred to as “elements”). Depending upon particularapplication, design constraints or other reasons, these elements may beimplemented using electronic hardware, computer program, or anycombination thereof.

The electronic hardware may include microprocessors, microcontrollers,digital signal processors (DSPs), field programmable gate arrays(FPGAs), programmable logic devices (PLDs), gated logic, discretehardware circuits, and other suitable hardware configured to perform thevarious functionality described throughout this disclosure. Computerprogram shall be construed broadly to mean instructions, instructionsets, code, code segments, program code, programs, subprograms, softwaremodules, applications, software applications, software packages,routines, subroutines, objects, executables, threads of execution,procedures, functions, etc., whether referred to as software, firmware,middleware, microcode, hardware description language, or otherwise.

The present application relates to the field of hearing devices, e.g.hearing aids.

U.S. Pat. No. 7,471,798 B2 and U.S. Pat. No. 9,301,049 B2 deal withlinear microphone arrays, extending a 2-microphone linear array to 3 ormore microphones with same microphone distance, assuming a target signalimpinging from the front of the user wearing the linear microphonearray.

Consider a hearing device utilizing beamforming to enhance the signal tonoise ratio (i.e. reducing unwanted background noise) while maintainingthe perception of the target (no target loss and unaltered spatialperception).

Beamformers in hearing devices commonly use two microphones. Increasingthe number of microphones can increase the degrees of freedom ofbeamformers in order to improve the enhancement.

Adaptive enhancement algorithms that use multiple microphones typicallyinvolve computationally expensive operations such as matrix inverse andeigenvalue decomposition of covariance matrices. The complexity in termsof operations per second will typically increase exponentially as afunction of the number of channels.

The main idea of this invention is to combine low complexity 2-channeladaptive beamformer structures in a meaningful way to achieve M-channeladaptive beamforming (where M>2) such as to maximize the beamformerenhancement performance as close to the M-channel full complexityreference as possible.

Two examples of an M=3 microphone configuration are: 1) a configurationwith front and rear microphones in a BTE shell and a third microphonesituated in the ear. 2) a configuration with a front and rear microphonein a BTE shell and the front microphone in a BTE shell on thecontra-lateral ear (binaural configuration).

An example of a M=4 microphone channel configuration is a configurationwith a front and rear microphone in a BTE shell, a third microphonesituated in the ear and a fourth microphone mounted in a BTE shell onthe contra-lateral ear or situated in the contra-lateral ear (binauralconfiguration).

An exemplary 2-channel adaptive beamformer building block (cf.‘two-channel beamformers’ (BF1, BF2, BF3, BF4, . . . ) in the followingdrawings) is an adaptive MVDR which aims at reducing the noise as muchas possible while maintaining the target. The latter is important inhearing aid context, since target loss with a few dB can haveconsequences for the audibility of the hearing aid user. The 2-channelbeamformer is implemented by applying complex weights in a signal pathwith complex sub-band analysis/synthesis filter banks. The complexweights are calculated based on a GSC structure. A GSC consists oftarget-adaptive enhanced omni and target cancelling beamformers and anoise-adaptive scalar β (for a 2-microphone implementation; for M>2, theadaptive parameter β is a vector (of size M−1)). The advantage of such abeamformer is that the behavior of the adaptive beamformer can becontrolled in the “beta-space” by simply constraining the value of betaover time, dependent on external parameters such as signal level andSNR. One microphone is defined as a reference microphone (providing areference input signal), i.e. the beamformer is preserving the targetsound as it is present in the reference microphone. Alternatively, avirtual microphone may be defined, and the signal provided by suchvirtual microphone used as reference input signal. In the latter case,the reference input signal an electric signal determined from the atleast three electric input signals as if provided by a (virtual)microphone located at a spatial reference point relative to locations ofthe at least three input transducers. An example of a two channelbeamformer as outlined above is shown in FIG. 5. A 2-channel beamformermay as well be implemented as filters in the time-domain.

The terms ‘beamformed signal’ and ‘spatially filtered signal’ are usedinterchangeably in the present disclosure with no intended difference inmeaning.

FIG. 1A shows a first embodiment of a hearing system comprising ahearing device (HD) comprising two cascaded two channel beamformersaccording to the present disclosure. FIG. 1A illustrates a 3-microphoneconfiguration with a cascade of two 2-channel beamformers. A hearingdevice (HD) located at an ear of a user comprises three microphones(denoted FM, RM, IM) A BTE part of the hearing device (HD) adapted forbeing located at the external ear (pinna) of the user comprises two ofthe three microphones, a front microphone (FM) and a rear microphone(RM), front and rear referring to a wearer's (=user's) normal lookdirection as ‘front’ and the opposite direction as ‘rear’. An ITE-partof the hearing device (HD) adapted for being located in or at the earcanal of the user comprises a microphone (IM) located in concha, at theear canal opening, or in the ear canal. The three microphones (FM, RM,IM) each pick up respective ‘samples’ of the sound field around the userand provide corresponding electric input signals (INFM, INRM, INIM). Inthe example of FIG. 1A, one of the BTE-microphones (here the frontmicrophone (FM)) is taken to be the reference microphone (as indicatedby the bold arrow representing the microphone signal INFM of the frontmicrophone (FM)). The signals (INFM, INRM) from the front and rearmicrophones (FM, RM) are fed to a two-channel beamformer BF1 providing a(first) beamformed signal (YBF1) as a (possibly complex) linearcombination of the (first and second) beamformer-input signals (INFM,INRM). The (first) beamformed signal (YBF1) is fed to a secondtwo-channel beamformer BF2 providing a resulting (second) beamformedsignal (YBF2) as a (possibly complex) linear combination of the (thirdand fourth) beamformer-input signals (YBF1, INIM). The resulting(second) beamformed signal (YBF2) is fed to a processor (HA-Pro) forapplying one or more further processing algorithms to the spatiallyfiltered signal (e.g. frequency and level dependent gain/attenuationaccording to the user's needs, e.g. to compensate for a hearingimpairment). The processor provides a processed signal (OUT) that is fedto an output transducer (OT), here a loudspeaker, for providing theprocessed signal (OUT) as stimuli perceivable by the user as sound (hereacoustic stimuli).

The system is configured to maintain a target signal in the signalpicked up by the reference microphone. The setup of FIG. 1A willprioritize placing a spatial null in the horizontal plane (wherein thetwo BTE-microphones (FM, RM) are located). This is reflected in thefirst beamformed signal YBF1 provided by the primary beamformer (BF1)receiving the reference signal Residual noise is further reduced by asecondary beamformer (BF2) based on the beamformed signal (YBF1) and thesignal (INIM) from the microphone (IM) at or in the ear canal of theuser.

Compared to a full three channel beamformer, the present cascade oftwo-channel beamformers has a computational advantage (the number ofcomputations increases exponentially with M, the number of beamformerinputs (microphones)). A further advantage is that the control of theadaptive parameter of the (M−1) two-channel beamformers (two independentβ-values, e.g. β1 and β2 for the first and second two-channelbeamformers (BF1, BF2), respectively) is computationally easier than thecontrol of the β-vector for an M-channel beamformer (for M>2).

FIG. 1B shows a second embodiment of a hearing system comprising threeinput transducers and two cascaded two channel beamformers according tothe present disclosure. The embodiment of FIG. 1B is similar to theembodiment of FIG. 1A in that it comprises a hearing device (HD)comprising a 3-microphone configuration (FM, RM, IM) combined in acascade of 2-channel beamformers (BF1, BF2) to provide a resultingspatially filtered signal (YBF2). The BTE-front microphone (FM) is thereference microphone (as in FIG. 1A). As a difference to the embodimentof FIG. 1A, the ITE-front microphone (IM) is fed to the primary (first)two channel beamformer (BF1) together with the reference signal (INFM)from the front microphone (FM) providing the first beamformed signal(YBF1). The secondary (second) two-channel beamformer (BF2) receives asinputs the first beamformed signal (YBF1) and the rear microphone signal(INRM) and provides the resulting beamformed signal (YBF1), which is fedto the processor (HA-Pro) for further processing, etc. (as in FIG. 1A).

This setup will prioritize placing a spatial null in the vertical planeand residual noise is further reduced by the secondary beamformer (BF2).The configuration in FIG. 1A is preferred over the configuration in FIG.1B, since (it is assumed that) the target sound will primarily beimpinging from the front direction (0 deg. azimuth), and experimentshave shown that this configuration approximates a 3-channel adaptiveMVDR beamformer very well (MVDR=minimum variance distortionlessresponse).

FIG. 1C shows a third embodiment of a hearing system comprising threeinput transducers and two cascaded two channel beamformers according tothe present disclosure. The embodiment of FIG. 1C is similar to theembodiment of FIG. 1A in that it comprises a hearing device (HD)comprising a 3-microphone configuration (FM, RM, IM) combined in acascade of 2-channel beamformers (BF1, BF2) to provide a resultingspatially filtered signal (YBF2). As a difference to the embodiment ofFIG. 1A, the ITE-front microphone (IM) is the reference microphone inthe embodiment of FIG. 1C. In the embodiment of FIG. 1C, the referencemicrophone signal (INIM) and the rear microphone signal (INRM) are fedto the first two-channel beamformer (BF1) providing the first beamformedsignal (YBF1). The first beamformed signal (YBF1), together with thefront microphone signal (INFM) are fed to the second two-channelbeamformer (BF2) providing the resulting (second) beamformed signal(YBF2), which is fed to the hearing device processor HA-Pro for furtherprocessing, etc. (as discussed in connection with FIG. 1A).

The benefit of this configuration is the preservation of pinna cues. Thecoupling of the signal (INFM) from the front microphone (FM) and thesignal (INRM) from the rear microphone (RM) to the first and secondbeamformers (BF1, BF2) can be interchanged.

FIG. 1D shows a first embodiment of a hearing system comprising threeinput transducers and three channel beamformers according to the presentdisclosure. FIG. 1D illustrates a further example of a 3-microphoneconfiguration of a hearing system, e.g. a hearing device. The hearingsystem comprises a tree-structure of three 2-channel beamformers (BF1,BF2, BF3). The BTE-front microphone (FM) is the reference microphone. Asa difference to the embodiment of FIG. 1A, the embodiment of FIG. 1Dcomprises an additional (primary) two-channel beamformer (BF3), whichreceives the reference microphone signal INFM (from front microphone FM)and the electric input signal (INIM) from the ITE-microphone (IM). Theadditional two-channel beamformer (BF3) provides spatially filteredsignal YBF3 as a (possibly complex) linear combination of thebeamformer-input signals (INFM, INIM). Instead of the electric inputsignal (INIM) from the ITE-microphone (IM), the second two channelbeamformer (BF2) of FIG. 1D receives the third spatially filtered signal(YBF3) as beamformer input together with the first beamformed signal(YBF1) to thereby provide the resulting beamformed signal (YBF2).

At the cost of somewhat increased computational complexity, the twoprimary beamformers (BF1, BF3) will reduce noise individually and thesecondary beamformer (BF2) will attenuate any residual noise further.Both primary beamformer outputs (YBF1 and YBF3, respectively) could bethe reference of the secondary beamformer (BF2). A similar configurationcould be made, where the microphone in the ear (IM) is the reference.

FIG. 1E shows a second embodiment of a hearing system comprising threeinput transducers and three channel beamformers according to the presentdisclosure. The embodiment of FIG. 1E is similar to the embodiment ofFIG. 1D. The difference is that the electric input signal

INIM from the ITE-microphone (IM) is the reference signal (instead ofthe electric input signal INFM from the front-microphone (FM) of theBTE-part of the hearing device in FIG. 1D). This has the advantage ofincluding the spatial cues of pinna in the first (and second) beamformedsignal(s) (YBF1, YBF2).

FIG. 2A shows an embodiment of a hearing system comprising first andsecond hearing devices (HD1, HD2) according to the present disclosure.The first and second hearing devices are adapted for being located atthe right and left ears, respectively, of a user. A 3-microphonebinaural configuration is illustrated with a cascade of two 2-channelbeamformers in each hearing device. The configuration of each of thefirst and second hearing devices (HD1, HD2) are similar to theembodiment of a hearing device shown in and discussed in connection withFIG. 1A. The front microphone (FN1, FM2) of the first and second hearingdevices (HD1, HD2), respectively, is the reference microphone (as inFIG. 1A). The secondary beamformer (BF2, BF4), respectively, is abinaural beamformer, attenuating the residual noise and providingrespective resulting beamformed signals YBF2, YBF4 that are fed torespective hearing aid processors (HA-Pro1, HA-Pro2) whose respectiveoutputs are fed to respective output transducers (OT1, OT2) as discussedin connection with FIG. 1. The respective binaural beamformers (BF2,BF4) receive a signal (INFM1, INFM2) from the front microphone (FM1,FM2) of the respective opposite hearing device (as opposed to the signalINIM from the ITE-microphone as shown in FIG. 1A). This will bepreferred when the target is in the front. When the target is impingingfrom the side (90 or 270 degrees azimuth), it is preferred to apply thebinaural beamformer first and use the rear microphone in the secondarybeamformer.

FIG. 2B shows a second embodiment of a hearing system comprising firstand second hearing devices according to the present disclosure,specifically suitable for pick up of a user's own voice. The hearingsystem of FIG. 2B uses as inputs to the respective primary 2-channelbeamformers BF1 and BF3 (of the first and second hearing devices,respectively) the ITE-microphone signals (INIM1 and INIM2) as referencesignals and provides the respective front microphone signals INFM1 andINFM2 (of the BTE-parts) as the second beamformer-input signals. It isassumed that the primary 2-channel beamformers BF1 and BF2 work in thefrequency (sub-band) domain and each provides respective beamformedsignals YBF1F and YBF3F also in the frequency domain. For simplicity,the beamformed signals YBF1F and YBF3F are transformed to time domainsignals YBF1 and YBF3 in respective synthesis filter banks (FBS). In theexemplary embodiment of FIG. 2B, the further processing to provide theown voice signal is performed in the first hearing device (HD1). Hencethe time domain beamformed signal YBF3 from primary 2-channelbeamformers BF3 of the second hearing device(HD2) is fed to antenna andtransceiver circuitry (not shown) and transmitted to and received byappropriate antenna and transceiver circuitry (not shown) in the firsthearing device (HD1), as indicated by dotted arrow YBF3. The twobeamformed (time domain) signals YBF1 and YBF3 are fed to a two-channelfrequency-domain beamformer (BF2) (including conversion from time- tofrequency-domain signals) providing beamformed signal YBF2F comprisingan estimate of the users own voice in the frequency domain. Thebeamformed signal YBF2F is fed to a synthesis filter bank (FBS) and theresulting estimate of the user's own voice (OV) in the time-domain isfed to transceiver TX and transmitted to another device, e.g. to acommunications device, e.g. a telephone. An advantage of using thecombination of a BTE-microphone and an ITE-microphone as the twobeamformer-input signals to the respective primary beamformers (BF1,BF2) of the first and second hearing devices (HD1, HD2) is that therespective microphone axes point downwards (or upwards), e.g. towardsthe mouth of the user. Hence such beamformers are suitable formaintaining a signal originating from the user's mouth (or moregenerally in directions perpendicular to a horizontal plane). Targetdirections in the horizontal plane are e.g. served by a microphoneconfiguration using the two BTE-microphones as inputs to the primary2-channel beamformer(s).

FIG. 3 shows an embodiment of a hearing system comprising fourmicrophones (A, B, C, D) according to the present disclosure. The4-microphone configuration provides options for several meaningfulcombinations of microphone order, and beamformer cascading structures,which can effectively approximate the performance of a full 4-microphonebeamformer. Consider microphone placements in the xyz orthogonalcoordinate system of the top right part of FIG. 3, where A=Front,B=Rear, C=Contralateral Front and D=In the Ear. In this example, thefront microphone (A) is the reference microphone (placed in (0, 0, 0)).Dependent on the target direction, one of the microphones B (target inx-direction), C (target in y-direction) or D (target in z-direction) isthe secondary input of the primary, secondary (BF3) and tertiary (BF2)beamformer (cf. indication by bold, dashed arrows in the lower part ofFIG. 3 of the different categories, ‘primary’, ‘secondary’, ‘tertiary’,. . . , of the layered structure of 2-channel beamformers indicated). Afading algorithm (Cross/Cov DOA Estim-unit) can adaptively control whichof the microphones B, C or D is the secondary input of the primary(BF1), secondary (BF3) or tertiary (BF2) beamformer. Fading can becontrolled based on the covariance C(AB,target), C(AC,target) andC(AD,target) and/or derivatives thereof, for example DOA estimates. Thefading algorithm (Cross/Cov DOA Estim-unit) receives all four microphonesignals (A, B, C, D) and based thereon determines a target direction(e.g. a target sound source comprising speech). The resulting controlsignal (Fading gains) is fed to a switching unit (Priority FadingSwitch) which—based on the determined location of or direction to thetarget sound source—sets respective switches to route electric inputsignals (B, C, D) to the appropriate ones of the two-channel beamformers(BF1, BF2, BF3).

In another embodiment, only one (primary) two-channel beamformer isactive at a given point in time (e.g. in a specific mode of operation;e.g. to same power). In this mode, the second beamformer-input signal(in addition to the reference input signal) to the primary two-channelbeamformer (BF1) is adaptively selected by the fading algorithm(Cross/Cov DOA Estim-unit) the switching unit (Priority Fading Switch).In this embodiment, the resulting beamformed signal (e.g. YBF1) is thenfed directly to the processor HA-Pro for further hearing aid processing.

FIG. 4 shows an embodiment of a hearing device according to the presentdisclosure. The hearing device (HD), e.g. a hearing aid, is of aparticular style (sometimes termed receiver-in-the ear, or RITE, style)comprising a BTE-part (BTE) adapted for being located at or behind anear of a user, and an ITE-part (ITE) adapted for being located in or atan ear canal of the user's ear and comprising a receiver (loudspeaker).The BTE-part and the ITE-part are connected (e.g. electricallyconnected) by a connecting element (IC) and internal wiring in the ITE-and BTE-parts (cf. e.g. wiring Wx in the BTE-part). The connectingelement may alternatively be fully or partially constituted by awireless link between the BTE- and ITE-parts.

In the embodiment of a hearing device in FIG. 4, the BTE part comprisestwo input units comprising respective input transducers (e.g.microphones) (FM, RM), each for providing an electric input audio signalrepresentative of an input sound signal (SBTE) (originating from a soundfield S around the hearing device). The input unit further comprises twowireless receivers (WLR1, WLR2) (or transceivers) for providingrespective directly received auxiliary audio and/or control inputsignals (and/or allowing transmission of audio and/or control signals toother devices, e.g. a remote control or processing device). The hearingdevice (HD) comprises a substrate (SUB) whereon a number of electroniccomponents are mounted, including a memory (MEM) e.g. storing differenthearing aid programs (e.g. parameter settings defining such programs, orparameters of algorithms, e.g. optimized parameters of a neural network)and/or hearing aid configurations, e.g. input source combinations (FM,RM, IM, WLR1, WLR2), e.g. optimized for a number of different listeningsituations. In a specific mode of operation, one or more directlyreceived auxiliary electric signals are used together with one or moreof the electric input signals from the microphones to provide abeamformed signal provided by applying appropriate complex weights tothe respective signals.

The substrate further comprises a configurable signal processor (DSP,e.g. a digital signal processor, e.g. including a processor for applyinga frequency and level dependent gain, e.g. providing beamforming, noisereduction, filter bank functionality, and other digital functionality ofa hearing device according to the present disclosure). The configurablesignal processor (DSP) is adapted to access the memory (MEM) and forselecting and processing one or more of the electric input audio signalsand/or one or more of the directly received auxiliary audio inputsignals, based on a currently selected (activated) hearing aidprogram/parameter setting (e.g. either automatically selected, e.g.based on one or more sensors, or selected based on inputs from a userinterface). The mentioned functional units (as well as other components)may be partitioned in circuits and components according to theapplication in question (e.g. with a view to size, power consumption,analogue vs. digital processing, etc.), e.g. integrated in one or moreintegrated circuits, or as a combination of one or more integratedcircuits and one or more separate electronic components (e.g. inductor,capacitor, etc.). The configurable signal processor (DSP) provides aprocessed audio signal, which is intended to be presented to a user. Thesubstrate further comprises a front-end IC (FE) for interfacing theconfigurable signal processor (DSP) to the input and output transducers,etc., and typically comprising interfaces between analogue and digitalsignals. The input and output transducers may be individual separatecomponents, or integrated (e.g. MEMS-based) with other electroniccircuitry.

The hearing device (HD) further comprises an output unit (e.g. an outputtransducer) providing stimuli perceivable by the user as sound based ona processed audio signal from the processor or a signal derivedtherefrom. In the embodiment of a hearing device in FIG. 4, the ITE partcomprises the output unit in the form of a loudspeaker (also termed a‘receiver’) (SPK) for converting an electric signal to an acoustic (airborne) signal, which (when the hearing device is mounted at an ear ofthe user) is directed towards the ear drum (Ear drum), where soundsignal (SED) is provided. The ITE-part further comprises a guidingelement, e.g. a dome, (DO) for guiding and positioning the ITE-part inthe ear canal (Ear canal) of the user. The ITE-part further comprises afurther input transducer, e.g. a microphone (IM), for providing anelectric input audio signal representative of an input sound signal(SITE) at the ear canal.

The electric input signals (from input transducers FM, RM, IM) may beprocessed in the time domain or in the (time-) frequency domain (orpartly in the time domain and partly in the frequency domain asconsidered advantageous for the application in question) using one ormore two-channel beamformers as proposed in the present disclosure

The hearing device (HD) exemplified in FIG. 4 is a portable device andfurther comprises a battery (BAT), e.g. a rechargeable battery, e.g.based on Li-Ion battery technology, e.g. for energizing electroniccomponents of the BTE- and possibly ITE-parts. In an embodiment, thehearing device, e.g. a hearing aid, is adapted to provide a frequencydependent gain and/or a level dependent compression and/or atransposition (with or without frequency compression) of one or morefrequency ranges to one or more other frequency ranges, e.g. tocompensate for a hearing impairment of a user. The BTE-part may e.g.comprise a connector (e.g. a DAI or USB connector) for connecting a‘shoe’ with added functionality (e.g. an FM-shoe or an extra battery,etc.), or a programming device, or a charger, etc., to the hearingdevice (HD).

FIG. 5 shows an embodiment of an adaptive two-channel beamformer forproviding a beamformed signal based on two (microphone) beamformer-inputsignals. FIG. 1 shows a part of a hearing aid comprising first andsecond microphones (M1, M1) providing respective first and secondelectric input signals INM1 and INM2, respectively, and a two-channelbeamformer (BF) providing a beamformed signal YBF based on the first andsecond electric input signals (INM1, INM2). A direction from the targetsignal to the hearing aid is e.g. defined by the microphone axis andindicated in FIG. 5 by arrow denoted Target sound. The target directioncan be any direction, e.g. a direction to the user's mouth (to pick upthe user's own voice), or other directions to target signal source (e.g.to the side of or above the user). An adaptive beam pattern (Y (Y(k))),for a given frequency band k, k being a frequency band index, may beobtained by linearly combining an omnidirectionaldelay-and-sum-beamformer (O (O(k))) and a delay-and-subtract-beamformer(C (C(k))) in that frequency band. The omnidirectional signal from thedelay-and-sum-beamformer (O (O(k))) is provided as linear combination ofthe beamformer-input signals INM1*Wo1+INM2*Wo2. The signal from thedelay-and-subtract-beamformer (C (C(k))) is provided as a linearcombination of the beamformer-input signals INM1*Wc1+INM2*Wc2. Theweights Wo1, Wo2, Wc1, Wc2 are complex frequency dependent constants,e.g. stored in a memory (MEM) of the hearing device. The adaptive beampattern arises by scaling the delay-and-subtract-beamformer (C(k)) by acomplex-valued, frequency-dependent, adaptive scaling factor β(k)(generated by beamformer ABF) before subtracting it from thedelay-and-sum-beamformer (O(k)), i.e. providing the beam pattern Y,

Y(k)=O(k)−β(k)C(k).

It should be noted that the sign in front of β(k) might as well be +, ifthe sign(s) of the weights constituting the delay-and-subtractbeamformer C is appropriately adapted. Further, β(k) may be substitutedby β*(k), where * denotes complex conjugate, such that the beamformedsignal Y_(BF) is expressed as Y_(BF)=(w_(o)(k)−β(k)·w_(c)(k))^(H)·IN(k).

The two-channel beamformer (BF) is e.g. adapted to work optimally insituations where the microphone signals consist of a localized targetsound source in the presence of additive noise sources. Given thissituation, the scaling factor β(k) (β in FIG. 5) is adapted to minimizethe noise under the constraint that the sound impinging from the targetdirection (at least at one frequency) is essentially unchanged. For eachfrequency band k, the adaptation factor β(k) can be found in differentways. The solution may be found in closed form as

${{\beta (k)} = \frac{\langle{C^{*}O}\rangle}{\langle{C}^{2}\rangle}},$

where * denote the complex conjugation and

denotes the statistical expectation operator, which may be approximatedin an implementation as a time average. The expectation operator

may be implemented using e.g. a first order IIR filter, possibly withdifferent attack and release time constants. Alternatively, theexpectation operator may be implemented using an FIR filter. Theadaptive 2-channel beamformer may e.g. be a Minimum VarianceDistortionless Response (MVDR) type beamformer, as e.g. described in[Brandstein & War& 2001] (Chapter 2.3 Eq. 2.25).

In a further embodiment, the adaptive 2-channel beamformer is configuredto determine the adaptation parameter β_(opt)(k) from the followingexpression

${\beta_{opt} = \frac{w_{O}^{H}C_{v}w_{C}}{w_{C}^{H}C_{v}w_{C}}},$

where w_(O) and w_(C) are the beamformer weights for the delay and sum Oand the delay and subtract C beamformers, respectively, C_(v) is thenoise covariance matrix, and H denotes Hermitian transposition. Suchbeamformer has a generalized sidelobe canceller structure, GSC.

For comparison, in an M>2 GSC beamformer, the β−parameter is an (M−1)×1size vector, defined by

β_(opt)=(W _(C) ^(H) C _(v) W _(C))⁻¹ W _(C) ^(H) C _(v) W _(O),

where W_(C) ^(H) is known as a size (M−1)×M blocking matrix and W_(o) isan M×1 beamformer vector. The main influence on the complexity is the(M−1) size matrix inverse operation, which is more expensive than M−1divisions.

FIG. 6 shows an embodiment of an M-input hearing system comprising M−1cascaded two-channel beamformers, each M−1-input transducer beingcoupled to an analysis filter bank to provide the electric input signalas a number of frequency sub-band signals. The hearing system of FIG. 6comprises a multitude M>2 input transducers each being coupled torespective analysis filter banks (FBA1, FBA2, . . . , FBAM) to providethe electric input signals (IN1, IN2, . . . , INM) from the inputtransducers (e.g. microphones) in a frequency sub-band (time-frequency)representation (IN1F, IN2F, . . . , INMF), which are fed to a beamformerfiltering unit (BFU) comprising a layered structure of cascaded2-channel beamformers (BF1, BF2, . . . , BFM−1, here in a prunedstructure; could be any other structure, e.g. a tree-like structure)according to the present disclosure (cf. ‘primary, ‘secondary’ and‘(M−1)ary’ indication of the individual layers in the top part of FIG.6). The beamformer filtering unit (BFU) provides a beamformed signal(YBFM−1) comprising a reference input signal, which is fed to aprocessor of the system (HA-Pro) for further processing. The processorprovides a processed output signal (OUTF), which is fed to a synthesisfilter bank (FBS) for conversion to a time domain signal (OUT). The timedomain output signal (OUT) is fed to an output transducer (OT) forproviding stimuli perceivable as sound to the user of the hearingsystem.

FIGS. 7A and 7B shows first and second exemplary location of threemicrophones (M1, M2, M3) in a BTE-part (BTE) of a hearing device (HD)according to the present disclosure. The embodiments of FIGS. 7A and 7Bboth resemble the BTE-part (BTE) of the embodiment of a hearing deviceshown in and discussed in connection with FIG. 4. The embodiments ofFIGS. 7A and 7B illustrate respective two different microphoneconfigurations. In FIG. 7A, the three microphones (M1, M2, M3) of theBTE-part are located on a straight line, as linear array (with uniformmicrophone distance) in the top part of the housing of the BTE-part. Themicrophone location is intended to provide that the microphone axispoints in a look direction of the user, when the user wears the hearingdevice (HD) at the ear (i.e. when the BTE-part is located at or behindthe external ear so that the microphone axis is located in a horizontalplane). In FIG. 7B, only two (M1, M2) of the three microphones of theBTE-part are located in the top part of the housing of the BTE-part,whereas the third microphone (M3) is located in the ‘bottom of thehousing of the BTE-part, close to the battery. The ‘off-axis-location’of the third microphone (M3) creates improved options for maintainingtarget signals from directions above or below a horizontal plane definedby the upper part of the external ears of the user (where the othermicrophones (M1, M2) are located. Other microphone placements and moremicrophones are possible and may be chosen according to the applicationin question with a view to expected locations of sound sources relativeto the user.

FIG. 8A illustrates an embodiment of a hearing system, e.g. a binauralhearing aid system, according to the present disclosure. The hearingsystem comprises left and right hearing devices in communication with anauxiliary device, e.g. a remote control device, e.g. a communicationdevice, such as a cellular telephone or similar device capable ofestablishing a communication link to one or both of the left and righthearing devices.

FIG. 8A, 8B together illustrate an application scenario comprising anembodiment of a binaural hearing aid system comprising first (right) andsecond (left) hearing devices (HD1, HD2) and an auxiliary device (AD)according to the present disclosure. The auxiliary device (AD) comprisesa cellular telephone, e.g. a SmartPhone. In the embodiment of FIG. 8A,the hearing devices and the auxiliary device are configured to establishwireless links (WL-RF) between them, e.g. in the form of digitaltransmission links according to the Bluetooth standard (e.g. BluetoothLow Energy, or equivalent technology). The links may alternatively beimplemented in any other convenient wireless and/or wired manner, andaccording to any appropriate modulation type or transmission standard,possibly different for different audio sources. The auxiliary device(e.g. a SmartPhone) of FIG. 8A, 8B comprises a user interface

(UI) providing the function of a remote control of the hearing aidsystem, e.g. for changing program or operating parameters (e.g. volume)in the hearing device(s), etc. The user interface (UI) of FIG. 8Billustrates an APP (denoted ‘target source location APP’) for selectinga mode of operation of the hearing system where a location of or adirection to a target sound source relative to the user (the left andright hearing devices (HD2, HD1) is or can be indicated. The APP allowsa user to select a manual (Manually), and automatic (Automatically) or amixed (Mixed) mode. In the screen of FIG. 8B, the manual mode ofoperation has been selected as indicated by the left solid ‘tick-box’and the bold face indication ‘Manually’. In this mode, the direction ofarrival of a target sound source is indicated manually by dragging asymbol ‘S’ to the current location. Alternatively, the location ordirection may be automatically determined (as described in the presentdisclosure). The resulting location or direction is displayed in thescreen by circular symbol denoted S and bold arrow denoted DoAschematically shown relative to the head of the user to reflect itsestimated location (here exemplified ‘to the right’ of the user). Thisis indicated by the text ‘Manually determined DoA to target source (S)’in the lower part of the screen in FIG. 8B. In a mixed mode (Mixed), theuser may indicate a rough direction to the target sound source (e.g. thequarter plane wherein the target sound source is located), and then thespecific direction of arrival is determined according to the presentdisclosure (whereby the calculations are simplified by excluding a partof the possible space).

In an embodiment, the calculations of the sound source location encodingparameter, e.g. a direction of arrival, are performed in the auxiliarydevice. In another embodiment, the calculations are performed in theleft and/or right hearing devices. In the latter case the system isconfigured to exchange the data defining location or the direction ofarrival of the target sound signal between the auxiliary device and thehearing device(s). The hearing device (HD1, HD2) are shown in FIG. 8A asdevices mounted at the ear (behind the ear) of a user (U). Other stylesmay be used, e.g. located completely in the ear (e.g. in the ear canal),fully or partly implanted in the head, etc. Each of the hearinginstruments comprise a wireless transceiver to establish an interauralwireless link (IA-WL) between the hearing devices, e.g. based oninductive communication or RF communication (e.g. Bluetooth technology).Each of the hearing devices further comprises a transceiver forestablishing a wireless link (WL-RF, e.g. based on radiated fields (RF))to the auxiliary device (AD), at least for receiving and/or transmittingsignals (AXS1, AXS2), e.g. control signals, e.g. information signals(e.g. DoA), e.g. including audio signals. The transceivers are indicatedby RF-IA-Rx/Tx-1 and RF-IA-Rx/Tx-2 in the right (HD1) and left (HD2)hearing devices, respectively.

FIG. 9 illustrates a n exemplary location of a virtual referencemicrophone (Virtual reference microphone) in a hearing device (HD)according to the present disclosure. The location, of the virtualreference microphone (relative to the ‘real’ microphones of the hearingdevice) is termed the reference point. The hearing device (HD) comprisesa BTE part adapted for being located at or in the external ear (pinna)of the user, and an ITE part adapted for being located at or in the earcanal of the user. The BTE-part comprises two (BTE1, BTE2) of the threemicrophones of the hearing device (HD). The ITE-part comprises the thirdmicrophone (ITE, here facing the environment). The three ‘physicalmicrophones (BTE1, BTE2, ITE) are indicated by solid (circular) dots.The (virtual) reference microphone is indicated by a dotted open circlebetween the two BTE-microphones (BTE1, BTE2).

It is intended that the structural features of the devices describedabove, either in the detailed description and/or in the claims, may becombined with steps of the method, when appropriately substituted by acorresponding process.

As used, the singular forms “a,” “an,” and “the” are intended to includethe plural forms as well (i.e. to have the meaning “at least one”),unless expressly stated otherwise. It will be further understood thatthe terms “includes,” “comprises,” “including,” and/or “comprising,”when used in this specification, specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. It will also be understood that when an element is referred toas being “connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element but an intervening element mayalso be present, unless expressly stated otherwise. Furthermore,“connected” or “coupled” as used herein may include wirelessly connectedor coupled. As used herein, the term “and/or” includes any and allcombinations of one or more of the associated listed items. The steps ofany disclosed method is not limited to the exact order stated herein,unless expressly stated otherwise.

It should be appreciated that reference throughout this specification to“one embodiment” or “an embodiment” or “an aspect” or features includedas “may” means that a particular feature, structure or characteristicdescribed in connection with the embodiment is included in at least oneembodiment of the disclosure. Furthermore, the particular features,structures or characteristics may be combined as suitable in one or moreembodiments of the disclosure. The previous description is provided toenable any person skilled in the art to practice the various aspectsdescribed herein. Various modifications to these aspects will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other aspects.

The claims are not intended to be limited to the aspects shown herein,but is to be accorded the full scope consistent with the language of theclaims, wherein reference to an element in the singular is not intendedto mean “one and only one” unless specifically so stated, but rather“one or more.” Unless specifically stated otherwise, the term “some”refers to one or more.

Accordingly, the scope should be judged in terms of the claims thatfollow.

REFERENCES

-   U.S. Pat. No. 7,471,798 B2. Microphone Array Having a Second Order    Directional Pattern, D. M. Warren, Knowles Electronics, Published    Feb. 5, 2004.-   U.S. Pat. No. 9,301,049 B2. Noise-reducing Directional Microphone    Array, G. W. Elko, M. Meyer, F. Gaensler, M H Acoustic LLC,    Published Jan. 10, 2013.-   EP3413589A1. “A microphone system and a hearing device comprising a    microphone system”. Oticon A/S. Published Jun. 6, 2018.-   [Brandstein & Ward; 2001] M. Brandstein and D. Ward, “Microphone    Arrays”, Springer 2001.

1. A hearing system comprising a first hearing device, e.g. a hearingaid, the first hearing device being configured to be worn at or in afirst ear of a user, or to be fully or partially implanted in the headof the user at the first ear, the hearing system comprising at leastthree input transducers configured to convert sound in the environmentof the first hearing device, or the hearing system, to respective atleast three electric input signals, one of which being selected as areference input transducer providing a reference input signal, or areference input signal being defined by an electric signal determinedfrom said at least three electric input signals as if provided by amicrophone located at a spatial reference point relative to locations ofsaid at least three input transducers; at least two adaptive 2-channelbeamformers, each providing a spatially filtered signal based on firstand second beamformer-input signals, wherein said adaptive 2-channelbeamformers maintain unit amplitude and phase for a target component ofsaid reference input signal; said at least two 2-channel beamformersbeing coupled in a layered structure at least comprising a primary layerand a secondary layer, where said primary layer comprises at least oneof said at least two 2-channel beamformers, termed primary 2-channelbeamformer(s); and wherein said secondary layer comprises at leastanother one of said at least two 2-channel beamformers, termed secondary2-channel beamformer(s); said at least two 2-channel beamformerscomprising a first primary 2-channel beamformer, wherein said firstbeamformer-input signal is said reference input signal, and wherein saidsecond beamformer-input signal is selected among the remaining electricinput signals, said first primary 2-channel beamformer providing aprimary spatially filtered reference signal; and a first secondary2-channel beamformer, wherein said first beamformer-input signal is saidprimary spatially filtered reference signal, and wherein said secondbeamformer-input signal is selected among a) those of said at leastthree electric input signals, which are not used as inputs to said firstprimary 2-channel beamformer, and b) a primary spatially filtered signalfrom a possible further primary 2-channel beamformer, said firstsecondary 2-channel beamformer providing a secondary spatially filteredreference signal, and wherein an adaptive parameter of a given 2-channelbeamformer is determined from the first and second beamformer-inputsignals for said 2-channel beamformer.
 2. A hearing system according toclaim 1 wherein said hearing system comprises at least three inputtransducers, which when worn by the user are located two and two onfirst, second and third straight lines, which together form a triangle.3. A hearing system according to claim 2 wherein at least two of saidthree input transducers are located on a straight line having anextension in a direction towards a mouth of the user, when the userwears the hearing system as intended.
 4. A hearing system according toclaim 1 comprising a second hearing device, e.g. a hearing aid, thesecond hearing device being configured to be worn at or in a second earof the user, or to be fully or partially implanted in the head of theuser at the second ear, wherein at least one of said at least threeinput transducers is located in the second hearing device.
 5. A hearingsystem according to claim 1 comprising a detection unit for determininga sound source location encoding parameter indicative of a location ofor a direction of arrival to said target sound source.
 6. A hearingsystem according to claim 5 wherein said detection unit is configured todetermine said sound source location encoding parameter as or based on acovariance estimate between said electric input signals.
 7. A hearingsystem according to claim 1 comprising a user interface allowing a userto indicate a location of or a direction of arrival to said target soundsource.
 8. A hearing system according to claim 1 comprising a controllerfor automatically selecting said second beamformer-input signals of thefirst primary and first secondary 2-channel beamformers, respectively.9. A hearing system according to claim 5 configured to provide that saidsecond beamformer-input signals of the first primary and first secondary2-channel beamformers, respectively, are determined from said soundsource location encoding parameter or from a user indication on saiduser interface.
 10. A hearing system according to claim 1 comprising amemory comprising corresponding values of a) a target sound sourcelocation or direction of arrival and b) appropriate couplingconfigurations of the available input transducers to two channelbeamformers.
 11. A hearing system according to claim 1 wherein saidfirst and/or said second hearing device is/are constituted by orcomprises a hearing aid, a headset, an earphone, an ear protectiondevice or a combination thereof.
 12. A hearing system according to claim1 comprising an auxiliary device, the hearing system being adapted toestablish a communication link between the hearing device or hearingdevices and the auxiliary device to provide that information, e.g.control and status signals, and possibly audio signals, can be exchangedor forwarded from one to the other.
 13. A hearing system according toclaim 12 when referring to claim 7 wherein the auxiliary devicecomprises said user interface.
 14. A hearing system as claimed in claim1 wherein the 2-channel beamformer is optimized as a hardware block. 15.A hearing system according to claim 1 wherein the layered structure of2-channel beamformers comprises more than two layers, primary,secondary, tertiary, etc.
 16. A hearing system according to claim 15wherein in a three-layered structure, the secondary spatially filteredreference signal is used as a first beamformer-input signal to a firsttertiary 2-channel beamformer, etc.
 17. A hearing system according toclaim 1 configured to provide that the direction to the target soundsource as experienced at the reference input is maintained through thecascaded 2-channel beamformer structure so that target signal componentsremain unchanged.
 18. A non-transitory application, termed an APP,comprising executable instructions configured to be executed on anauxiliary device to implement a user interface for a hearing systemaccording to claim
 1. 19. An audio processing system comprising at leastthree input transducers configured to convert sound in the environmentof the audio processing system, to respective at least three electricinput signals, one of which being selected as a reference inputtransducer providing a reference input signal, or a reference inputsignal being defined by an electric signal determined from said at leastthree electric input signals as if provided by a microphone located at aspatial reference point relative to locations of said at least threeinput transducers; at least two adaptive 2-channel beamformers, eachproviding a spatially filtered signal based on first and secondbeamformer-input signals, wherein said adaptive 2-channel beamformersmaintain unit amplitude and phase for a target component of saidreference input signal; said at least two 2-channel beamformers beingcoupled in a cascaded structure at least comprising a primary layer anda secondary layer, where said primary layer comprises at least one ofsaid at least two 2-channel beamformers, said at least one 2-channelbeamformer of the primary layer being termed primary 2-channelbeamformer(s); and wherein said secondary layer comprises at leastanother one of said at least two 2-channel beamformers, said at leastone 2-channel beamformer of the second layer being termed secondary2-channel beamformer(s); said at least two 2-channel beamformerscomprising a first primary 2-channel beamformer, wherein said firstbeamformer-input signal is said reference input signal, and wherein saidsecond beamformer-input signal is selected among the remaining electricinput signals, said first primary 2-channel beamformer providing aprimary spatially filtered reference signal; and a first secondary2-channel beamformer, wherein said first beamformer-input signal is saidprimary spatially filtered reference signal, and wherein said secondbeamformer-input signal is selected among a) those of said at leastthree electric input signals, which are not used as inputs to said firstprimary 2-channel beamformer, and b) a primary spatially filtered signalfrom a possible further primary 2-channel beamformer, said firstsecondary 2-channel beamformer providing a secondary spatially filteredreference signal, and wherein an adaptive parameter of a given 2-channelbeamformer is determined from the first and second beamformer-inputsignals for said 2-channel beamformer.
 20. A method of operating anaudio processing device or system, e.g. a hearing device or a hearingsystem, the method comprising providing at least three electric inputsignals representative of sound in the environment of the audioprocessing device or system, one of which being selected as a referenceinput providing a reference input signal, or a reference input signalbeing defined by an electric signal determined from said at least threeelectric input signals as if provided by an input located at a spatialreference point relative to locations of inputs providing said at leastthree electric input signals; providing at least two adaptive 2-channelbeamformers, each providing a spatially filtered signal based on firstand second beamformer-input signals, wherein said adaptive 2-channelbeamformers maintain unit amplitude and phase for a target component ofsaid reference input signal; and providing that said at least two2-channel beamformers are coupled in a cascaded structure at leastcomprising a primary layer and a secondary layer, providing that saidprimary layer comprises at least one of said at least two 2-channelbeamformers, said at least one beamformer of the primary layer beingtermed primary 2-channel beamformer(s); and providing that saidsecondary layer comprises at least another one of said at least two2-channel beamformers, said at least one beamformer of the second layerbeing termed secondary 2-channel beamformer(s). providing that said atleast two adaptive 2-channel beamformers comprise a first primary2-channel beamformer, wherein said first beamformer-input signal is saidreference input signal, and wherein said second beamformer-input signalis selected among the remaining electric input signals, said firstprimary 2-channel beamformer providing a primary spatially filteredreference signal; and a first secondary 2-channel beamformer, whereinsaid first beamformer-input signal is said primary spatially filteredreference signal, and wherein said second beamformer-input signal isselected among a) those of said at least three electric input signals,which are not used as inputs to said first primary 2-channel beamformer,and b) a primary spatially filtered signal from a possible furtherprimary 2-channel beamformer, said first secondary 2-channel beamformerproviding a secondary spatially filtered reference signal, anddetermining an adaptive parameter of a given 2-channel beamformer fromthe first and second beamformer-input signals for said 2-channelbeamformer.